1. Technical Field
The present invention generally relates to an information searching system and more particularly, to a mark detecting apparatus for detecting marks recorded on frames of a micro-roll film for use in a reader/printer or the like.
2. Prior Art
In a reader/printer or the like, it is so arranged that retrieval of information recorded frames of a micro-roll film is effected for re-utilization of the information. For a system of such retrieval, there has conventionally been employed an arrangement in which marks (blip marks or document marks) having a density different from that of a film base are photographically formed in a non-image portion at a side edge portion of the film in positions corresponding to respective frames, so that by counting such marks with photoelectric and electric counting means as the film is driven, the film is stopped when the count value coincides with the desired frame number, thereby to retrieve the necessary information recorded frame.
In FIGS. 1 and 2, there is shown one example of the mark detecting apparatus of the above described type. In a mark detecting mechanism thereof shown in FIG. 1, a film 1 is arranged to be displaceable in any of a forward direction or a reverse direciton, while marks 2 are photographically recorded on a non-image portion at one side edge portion of the film 1 so as to correspond in position to respective frames 3. Above and adjacent to the one side edge of the film 1 and in position confronting a passage of the marks 2, a pair of photoelectric elements 4 and 5 are provided side by side to be aligned with the direction of movement of the film 1, whereby light projected onto the photoelectric elements 4 and 5 from a light source 6 through the film 1 is intermittently intercepted due to passing of the marks 2.
In FIG. 2, one example of a circuit for processing signals obtained by the mark detecting mechanism of FIG. 1 is shown, in which circuit, photo-transistors are employed respectively for the photoelectric elements 4 and 5. Each of the photo-transistors has its collector connected to a power source +V, with respective emitters thereof being grounded through variable resistors 7 and 8. The emitter of the photo-transistor constituting the photoelectric element 4 is connected to a non-inverting input terminal of a voltage comparator 9 at a subsequent stage, while the emitter of the photo-transistor constituting the photoelectric element 5 is coupled to an inverting input terminal of another voltage comparator 10. A variable resistor 11 is intended to apply a reference voltage for the voltage comparators 9 and 10, and its one end is connected to the power source +V, the other end thereof to the ground, and its sliding terminal is coupled to the inverting input terminal of the voltage comparator 9 and the non-inverting input terminal of the voltage comparator 10.
Thus, in the voltage comparator 9, an L signal (low voltage signal) is provided when the light incident upon the photoelectric element 4 is intercepted by the mark 2, while on the contrary, an H signal (high voltage signal) is output when the light is permitted to be incident upon the photoelectric element 4. On the other hand, in the voltage comparator 10, an H signal is output when the light incident upon the photoelectric element 5 is intercepted by the mark 2, while an L signal is produced when the light is allowed to be incident upon the photoelectric element 5. At a stage subsequent to the voltage comparator 9, there are provided side by side a signal processing section 13a for detecting a falling or negative edge of the output of the comparator 9, and a signal processing section 13b for detecting a rising or positive edge of said output. The signal processing section 13a is constituted by a differentiation circuit including a capacitor 14, a pull-up resistor 15, and a diode 16 for protection against excessive voltages, and a Schmitt inverter buffer 17 at a subsequent stage, and produces pulses only when the output of said voltage comparator 9 is varied from the H level to the L level. Meanwhile, the signal processing section 13b is constituted by a differentiation circuit including a capacitor 18, a pull-down resistor 19 and a diode 20 for protection against inverse voltage, and a Schmidt buffer 21 at a subsequent stage, and produces pulses only when the output of the voltage comparator 9 is varied from the L level to the H level. The output terminal of the Schmitt inverter buffer 17 is connected to one input terminal 22a of an AND gate 22 at a subsequent stage, and a logical product of the output of the voltage comparator 10 connected to the other input terminal 22b and the output of the Schmitt inverter buffer 17 is obtained by said AND gate 22. On the other hand, the output terminal of the Schmitt buffer 21 is connected to one input terminal 23a of another AND gate 23, and a logical product of the output of the voltage comparator 10 connected to the other input terminal 23b and the output of the Schmidt buffer 21 is obtained at said AND gate 23.
In the known mark detecting apparatus as described so far, when the film 1 is displaced in the forward direction with respect to the interception of light incident upon the photoelectric elements 4 and 5 following the movement of the mark 2, the photoelectric element 4 is first intercepted, and then, the photoelectric element 5 is intercepted. In the states of mark detection as described above, the output of the voltage comparator 9 becomes the L signal, while that of the voltage comparator 10 is rendered to be the H signal, and therefore, in the detecting order as described above, the output of the AND gate 23 which provides the logical product of the output of the signal processing section 13b which produces the pulses at the positive edge of the output of the voltage comparator 9 and the output of the voltage comparator 10, becomes the H signal, whereby the mark detection in the case where the film 1 runs in the forward direction can be effected. It is to be noted here that since the output of the signal processing section 13a which produces the pulses at the negative edge of the voltage comparator 9 and the output of the voltage comparator 10 are not overlapped with each other in terms of time, no H signals are produced from the AND gate 22.
Similarly, in the case where the film 1 is caused to run in the reverse direction, the photoelectric element 5 is first intercepted, with a subsequent interception of the photoelectric element 4 in the order or light interception by the mark 2, and therefore, the output of the AND gate 22 which takes the logical product of the output of the signal processing section 13a and the output of the voltage comparator 10, becomes the H signal, whereby the mark detection in the case where the film 1 runs in the reverse direction may be achieved.
Thus, by counting the pulses produced from said AND gates 22 and 23, the desired frame can be retrieved.
As described so far, in the mark detecting apparatus of such a system, a plurality of photoelectric elements are required for the mark detection. In the foregoing example, the number of the photoelectric elements is two pieces, since the mark is limited to one kind, but if the kind of the mark is increased as in an example shown in FIGS. 3 and 4, it becomes necessary to employ a larger number of photoelectric elements.
However, the photoelectric conversion efficiency of the photoelectric elements tends to be largely scattered or deviated in the manufacture even in the same kind, and in the case where the plurality of photoelectric elements are to be employed as described above, it becomes necessary to provide adjusting means for each photoelectric element in order to bring the detecting performance between the photoelectric elements into agreement. In the circuit of FIG. 2, the variable resistors 7 and 8 are incorporated as said adjusting means.
On the other hands, there are provided various kinds of films, representative ones of which are the silver salt type, diazo type, vesicular type, etc., each different in the base density. Besides such a difference, since the image density to be recorded differs to a large extent according to the kinds of films, it is required to adjust the detecting performance of the photoelectric element to correspond to the kinds of films, and the adjusting work therefor includes a troublesome procedure. Especially, in the case of the vesicular type film, although a sufficient contrast may be obtained in a position where the image recorded on the film is projected through a lens and forms an image, the contrast becomes generally equal to a difference of a diffused density in a position very close to the film, and the contrast is extremely small. Accordingly, for the mark detection of such a film, it is necessary to effect the adjustment of the output performance of the photoelectric element still more carefully, with the adjusting work involved therefor becoming more and ,more troublesome.
Meanwhile, in the case where a light source for projecting the image of the film onto a screen or a light source for obtaining a hard copy is commonly used also for the light source for the mark detection, the intensity of the light source is varied so that the brightness at the image forming surface is not changed when the reproducing magnification of the image is to be altered, and therefore, in this case also, it is necessary to adjust the output performance with respect to each of the plurality of photoelectric elements.
FIGS. 3 and 4 show a mark detecting apparatus so arranged that three kinds of marks with different lengths, i.e. a small mark 2's, a medium mark 2'm, and a large mark 2'l, can be detected through employment of the detecting system as described above. As shown in FIG. 3, in this retrieval apparatus, four photoelectric elements 24a, 24b, 24c and 24d are arranged side by side so as to be aligned in the direction of running of the film, whereby the small mark 2's is detected by the combination of the photoelectric elements 24a and 24b, and the photoelectric element 24c together with the photoelectric elements 25a and 24b is employed for the detection of the middle mark 2'm, and the photoelectric element 24d is used for the detection of the large mark 2'l in combination with the photoelectric elements 24a, 24b and 24c. The photoelectric elements 24a and 24b are disposed in positions neighboring each other, so that they are simultaneously covered by the small mark 2's. The distance between the photoelectric elements 24a and 24c is made longer than the length of the small mark 2's, and shorter than the length of the large mark 2'l, and thus, the photoelectric elements 24a and 24c are adapted to be simultaneously covered by the medium mark 2'm. The distance between the photoelectric elements 24a and 24d is set to be longer than the length of the medium mark 2'm so that the photoelectric elements 24a and 24d are simultaneously covered by the large mark 2'l.
In FIG. 4 showing one example of the circuit for processing the mark detection signals obtained by the photoelectric elements 24a, 24b, 24c and 24d of FIG. 3, a circuit section 25 surrounded by a one dot chain line has a construction generally similar to that of FIG. 2 described earlier, and includes signal processing stages 26a and 26b respectively for detecting the positive edge and negative edge of the mark detection signal (which becomes the H level signal) by the photoelectric element 24a. When the marks pass the portion where the photoelectric elements 24a and 24b are provided in the forward direction, pulses corresponding thereto are produced from an AND gate 27, while on the contrary, when the marks pass there in the reverse direction, pulses corresponding thereto are produced from an AND gate 28. Here, in addition to the above circuit section 25, there are provided AND gates 29 and 30 which invert the mark detection signal of the photoelectric element 24c, and obtain a logical product of this inverted signal and the output of said AND gates 27 and 28, AND gates 31 and 32 which obtain a logical product of the detection signal of the photoelectric element 24c, the outputs of the AND gates 27 and 28, and the inverted output of the photoelectric element 24d, and AND gates 33 and 34 which obtain a logical product of the outputs of the photoelectric elements 24c and 24d and the outputs of the AND gates 27 and 28. By the above arrangement, from the AND gate 29, a small mark forward direction pulse, i.e. a pulse equivalent to the detection of the small mark 2's moving in the forward direction, may be obtained. Similarly, there are respectively obtained the small mark reverse direction pulse from the AND gate 30, medium mark forward direction pulse from the AND gate 31, medium mark reverse direction pulse from the AND gate 32, large mark forward direction pulse from the AND gate 33, and large mark reverse direction pulse from the AND gate 34.
As described earlier, it will be seen from the above example that if arranged as follows, the adjustment of the output performance for the photoelectric elements extends as far as four positions, with consequent troublesome procedures for the adjusting work.